The present invention relates to a semiconductor device and, in particular, relates to the semiconductor device which is favorably utilized in a field effect transistor using a nitride semiconductor.
The field effect transistor using the nitride semiconductor is operable at a high frequency and has high voltage withstand—low on-resistance characteristics. Therefore, the field effect transistor using the nitride semiconductor is excellent in high-speed switching operation performance and application of the field effect transistor to a switching power source, an inverter and so forth of a power electronics system, is expected.
For example, a normally-off type GaNFET is disclosed, for example, in Japanese Unexamined Patent Application Publication No. 2011-188178 (Japanese Patent No. 4968487). Then, it is disclosed that since a gate-to-source structure thereof is not an insulation structure as adopted in an existing silicon MOSFET as a feature of the normally-off type GaNFET, when an excessive gate drive voltage is applied to the GaNFET, a large current flows between the gate and the source. Therefore, it is disclosed that a series circuit which is configured by a voltage control circuit and a diode is coupled between the drain and the gate thereby to drive the transistor while suppressing a gate overvoltage applied to a wide bandgap semiconductor switch and without sacrificing switching characteristics and an on-resistance.